Browsing by Author "Gan, Fei"

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Cyanobacteriochrome-based photoswitchable adenylyl cyclases (cPACs) for broad spectrum light regulation of cAMP levels in cells
(2018-06) Blain-Hartung, Matthew; Rockwell, Nathan C.; Moreno, Marcus V.; Martin, Shelley S.; Gan, Fei; Bryant, Donald A.; Lagarias, J. Clark
Class III adenylyl cyclases generate the ubiquitous second messenger cAMP from ATP often in response to environmental or cellular cues. During evolution, soluble adenylyl cyclase catalytic domains have been repeatedly juxtaposed with signal-input domains to place cAMP synthesis under the control of a wide variety of these environmental and endogenous signals. Adenylyl cyclases with light-sensing domains have proliferated in photosynthetic species depending on light as an energy source, yet are also widespread in nonphotosynthetic species. Among such naturally occurring light sensors, several flavin-based photoactivated adenylyl cyclases (PACs) have been adopted as optogenetic tools to manipulate cellular processes with blue light. In this report, we report the discovery of a cyanobacteriochrome-based photoswitchable adenylyl cyclase (cPAC) from the cyanobacterium Microcoleus sp. PCC 7113. Unlike flavin-dependent PACs, which must thermally decay to be deactivated, cPAC exhibits a bistable photocycle whose adenylyl cyclase could be reversibly activated and inactivated by blue and green light, respectively. Through domain exchange experiments, we also document the ability to extend the wavelength-sensing specificity of cPAC into the near IR. In summary, our work has uncovered a cyanobacteriochrome-based adenylyl cyclase that holds great potential for the design of bistable photoswitchable adenylyl cyclases to fine-tune cAMP-regulated processes in cells, tissues, and whole organisms with light across the visible spectrum and into the near IR.
Extensive remodeling of a cyanobacterial photosynthetic apparatus in far-red light
(American Association for the Advancement of Science, 2014-08) Gan, Fei; Zhang, Shuyi; Rockwell, Nathan C.; Martin, Shelley; Langarias, J. Clark; Bryant, Donald A.; Gan, Fei; Zhang, Shuyi; Rockwell, Nathan C.; Martin, Shelley; Langarias, J. Clark; Bryant, Donald A.
Cyanobacteria are unique among bacteria in performing oxygenic photosynthesis, often together with nitrogen fixation and, thus, are major primary producers in many ecosystems. The cyanobacterium, Leptolyngbya sp. strain JSC-1, exhibits an extensive photoacclimative response to growth in far-red light that includes the synthesis of chlorophylls d and f. During far-red acclimation, transcript levels increase ≥2-fold for ~900 genes and decrease ≥2-fold for ~2000 genes. Core subunits of photosystem I, photosystem II, and phycobilisomes are replaced by proteins encoded in a 21-gene cluster that includes a knotless red/far-red phytochrome and two response regulators. This acclimative response enhances light harvesting for wavelengths complementary to the growth light (λ = 700 to 750 nm) and enhances oxygen evolution in far-red light.
Occurrence of Far-Red Light Photoacclimation (FaRLiP) in Diverse Cyanobacteria
(2014-12) Gan, Fei; Shen, Gaozhong; Bryant, Donald A.
Cyanobacteria have evolved a number of acclimation strategies to sense and respond to changing nutrient and light conditions. Leptolyngbya sp. JSC-1 was recently shown to photoacclimate to far-red light by extensively remodeling its photosystem (PS) I, PS II and phycobilisome complexes, thereby gaining the ability to grow in far-red light. A 21-gene photosynthetic gene cluster (rfpA/B/C, apcA2/B2/D2/E2/D3, psbA3/D3/C2/B2/ H2/A4, psaA2/B2/L2/I2/F2/J2) that is specifically expressed in far-red light encodes the core subunits of the three major photosynthetic complexes. The growth responses to far-red light were studied here for five additional cyanobacterial strains, each of which has a gene cluster similar to that in Leptolyngbya sp. JSC-1. After acclimation all five strains could grow continuously in far-red light. Under these growth conditions each strain synthesizes chlorophylls d, f and a after photoacclimation, and each strain produces modified forms of PS I, PS II (and phycobiliproteins) that absorb light between 700 and 800 nm. We conclude that these photosynthetic gene clusters are diagnostic of the capacity to photoacclimate to and grow in far-red light. Given the diversity of terrestrial environments from which these cyanobacteria were isolated, it is likely that FaRLiP plays an important role in optimizing photosynthesis in terrestrial environments.
Tables S1 and S2 [dataset]
(2014-08) Gan, Fei; Zhang, Shuyi; Rockwell, Nathan C.; Martin, Shelley; Langarias, J. Clark; Bryant, Donald A.
This dataset is associated with the following article: Gan, F., S. Zhang, N. C. Rockwell, S. S. Martin, J. C. Lagarias, and D. A. Bryant. “Extensive Remodeling of a Cyanobacterial Photosynthetic Apparatus in Far-Red Light." Science 345, no. 6202 (August 21, 2014): 1312-1317. doi:10.1126/science.1256963